This invention relates to an aluminosilicate zeolite designated UZM-9 having the LTA topology, but which is thermally stable in an acidic form and has high Si/Al ratio in the range of greater than 3.5 to about 6.0. The zeolite can be used as an adsorbent or an acid catalyst.
Zeolites are crystalline aluminosilicate compositions which are microporous and which consist of a negatively charged framework formed from corner sharing AlO2 and SiO2 tetrahedra. The negative framework charge is balanced by cations, which usually reside in the pores. Numerous zeolites, both naturally occurring and synthetically prepared are used in various industrial processes. Zeolites are characterized by having pore openings of uniform dimensions, having a significant ion exchange capacity, and being capable of reversibly desorbing an adsorbed phase which is dispersed throughout the internal voids of the crystal without significantly displacing any atoms which make up the permanent zeolite crystal structure.
One particular zeolite, designated zeolite A, was first disclosed in U.S. Pat. No. 2,882,243. The ""243 patent states that zeolite A has a Si/Al molar ratio of 0.67 to 1.17. U.S. Pat. No. 3,306,922 discloses a zeolite N-A which is identified as an ammonium or alkyl ammonium containing zeolite of LTA topology. The Si/Al ratio is stated to be in the range of 1.25 to 3.0. U.S. Pat. No. 3,314,752 discloses a zeolite identified as ZK-4 which is stated to be zeolite LTA topology with a mixture of methyl ammonium ion or hydronium ion and sodium or potassium. The Si/Al ratio in ZK-4 is stated to be between 1.25 and 2.0. In U.S. Pat. No. 3,375,205 a zeolite Alpha is disclosed which has the zeolite A type lattice but has a Si/Al ratio of greater than 2 to 3.5. Treatment of N-A by ammonium fluorosilicate to increase the Si/Al ratio is disclosed in U.S. Pat. No. 4,610,856. However, substantial loss in crystallinity (see, column 29, lines 1 to 35) with only a small increase in the Si/Al ratio (2.76 to 3.79) is reported. Finally, Fyfe et al. in J. Chem. Soc., Chem. Commun., 1093-1094 (1984) report dealumination of zeolite ZK-4, but with the formation of amorphous material.
In contrast to the above references, applicants have prepared a zeolite designated UZM-9 which has the zeolite A topology (LTA), but has a Si/Al ratio of greater than 3.5 to 6 in its as synthesized form. The UZM-9 can also be prepared with organoammonium cations larger than tetramethylammonium. Finally, UZM-9 is stable to calcination up to at least 600xc2x0 C. and is useful as a catalyst in its acid form.
As stated, the present invention relates to a new aluminosilicate zeolite designated UZM-9. Accordingly, one embodiment of the invention is a microporous crystalline zeolite having a three-dimensional framework of at least AlO2 and SiO2 tetrahedral units and an empirical composition on an as synthesized and anhydrous basis expressed by an empirical formula of:
Mmn+Rrp+Al1xe2x88x92xExSiyOz
where M is at least one exchangeable cation selected from the group consisting of alkali and alkaline earth metals, xe2x80x9cmxe2x80x9d is the mole ratio of M to (Al+E) and varies from 0 to about 0.95, R is at least two organic cations selected from the group consisting of quaternary ammonium ions, diquaternary ammonium ions, protonated amines, protonated alkanolamines and quaternized alkanolammonium ions and further where at least one of said organic cations contains an organic group having at least two carbon atoms, xe2x80x9crxe2x80x9d is the mole ratio of R to (Al+E) and has a value of about 0.5 to about 1.5, xe2x80x9cnxe2x80x9d is the weighted average valence of M and has a value of about 1 to about 2, xe2x80x9cpxe2x80x9d is the weighted average valence of R and has a value of about 1 to about 2, E is an element selected from the group consisting of gallium, iron, boron and mixtures thereof, xe2x80x9cxxe2x80x9d is the mole fraction of E and has a value from 0 to about 0.5, xe2x80x9cyxe2x80x9d is the mole ratio of Si to (Al+E) and varies from greater than 3.5 to about 6 and xe2x80x9czxe2x80x9d is the mole ratio of O to (Al+E) and has a value determined by the equation:
z=(mxc2x7n+rxc2x7p+3+4xc2x7y)/2
and is characterized in that it has the x-ray diffraction pattern having at least the d spacings and intensities set forth in Table A.
Another embodiment of the invention is a process for preparing the crystalline microporous zeolite described above. The process comprises forming a reaction mixture containing reactive sources of M, R, Al, Si and optionally E at a temperature of about 60xc2x0 C. to about 175xc2x0 C., the reaction mixture having a composition expressed in terms of mole ratios of the oxides of:
aM2/nO:bR2/pO:1-cAl2O3:cE2O3:dSiO2:eH2O
where xe2x80x9caxe2x80x9d has a value of 0.0 to about 1.50, xe2x80x9cbxe2x80x9d has a value of about 1.0 to about 25, xe2x80x9ccxe2x80x9d has a value of 0 to about 0.5, xe2x80x9cdxe2x80x9d has a value of about 4 to about 50 and xe2x80x9cexe2x80x9d has a value of about 25 to about 15000.
Yet another embodiment of the invention is a hydrocarbon conversion process using the above-described zeolite. The process comprises contacting the hydrocarbon with the zeolite at conversion conditions to give a converted hydrocarbon.
These and other objects and embodiments will become clearer after a detailed description of the invention.